This invention relates to developing apparatus for recording equipment wherein toner particles adhere to an electrostatic latent image or a magnetic latent image formed on the surface of an image-forming member by electrophotography, electrostatic recording, electrostatic printing, or magnetic recording. The device is useful for one or two component developers, both the contact and non-contact developing methods.
Conventionally, among the above contact type or non-contact type developing apparatus, such as the developing apparatus that so forms the developer layer on the developer carrier as not to heavily rub with the surface of the image forming member and causes the toner to adhere onto the latent image of the image forming member under the condition of the oscillating electric field, the developing apparatus using one-component developer has been known in the Japanese Patent Publication Open to Public Inspections, No. 18656.about.18659/1980 (hereinafter referred to as Japanese Patent O.P.I. Publication); the developing apparatus using two-component developer has been known in the Japanese Patent O.P.I. Publications, No. 144452/1981, No. 139761/1982, No. 147652/1982, No. 48065/1983, No. 181362/1984, and No. 222847/1984. In these developing apparatuses described above, unlike the developing apparatuses wherein the surface of the image-forming member comes into contact with and is heavily rubbed by the developer layer, since the developing is carried out under the oscillating electric field, sweeping marks on the toner image are not generated, and fogging is not apt to occur. Moreover, in the case where the developing is carried out under the non-contact condition, even if development is doubly conducted on the surface of the image-forming member on which a toner image is already formed, the previously formed toner image is not damaged, thus providing excellent recording equipment wherein a color image is formed by combining a plurality of toner images on the image-forming member. Furthermore, the developing apparatus using two-component developer, compared with that using one-component developer, has to keep a constant toner particle ratio of the developer and also has a problem that the carrier particles gradually deteriorate with time; however, frictional electrification control of the toner particles becomes easy, and no toner particle agglomeration is apt to occur, thus facilitating formation of a uniform developer layer on the surface of the developer carrier, and the magnetic particles do not have to be added in the toner. Consequently, the color of the toner image other than black and brown become clear, thus providing a excellent equipment for recording color images.
Even in the developing apparatus described above, nonuniformity or fogging of development may occur. To prevent these problems from occurring, it is effective to form a uniform and thin developer layer, and, by doing so, to reduce the clearance for development between the developer carrier and image-forming member and to increase the electric field strength.
In this respect, in the conventional developing apparatus that regulates the thickness of the developer layer by means of only a layer-thickness-regulating member forming a passage gate for the developer layer; due to the fluctuation of the magnetic field strength which makes the surface of the developer carrier adsorb the developer, the disadvantage that the agglomerated developer or waste is apt to clog the narrow clearance-regulating portion between the developer carrier and the layer-thickness-regulating member, and so on. The thinner the layer is regulated, the larger becomes the nonuniformity of the layer thickness; thus forming a uniform and thin developer is very difficult. This problem becomes more apparent because of some causes such as the tendency of the developer susceptible to agglomeration, especially when using toner particles and carrier particles, which are finer than the conventional carrier particles with an average diameter ranging from several tens .mu.m to several hundreds .mu.m or the conventional toner particles with an average diameter larger than several tens .mu.m, as the developer in order to obtain a high-quality image reproduced with variable density or delicate lines and points; thus, causing the problem that the nonuniformity in the regulation of the layer thickness is apt to result in development nonuniformity.
In a developing apparatus wherein the developer layer comes in contact with and rubs the surface of an image-forming member, the following two methods are known to be adopted according to the Japanese Utility Model Publication Open to Public Inspection No. 107336/1979 and No. 9797/1982 (hereinafter referred to as Japanese Model Utility O.P.I. Publication): The one method is that a magnetic piece is mounted on the layer-thickness-regulating made of non-magnetic material in order to prevent problems such as fogging caused by fly toner particles which are generated when the depressed developer layer expands after passing the layer-thickness-regulating member; the other method is that a blade made of non-magnetic material is mounted which comes in contact with the developer layer that has just passed the layer-thickness-regulating member and provides the toner particles with static electrification in order to prevent the toner particles of the developer layer which has passed the layer-thickness-regulating member from flying because of static-electrification shortage, and in order to prevent the toner particles from causing fogging.
The inventors have studied and improved the above-mentioned methods, they have obtained the result that a smoothing member which makes the layer thickness uniform by touching the developer layer should be positioned near the development area instead of just after the layer-thickness-regulating member in order to obtain a uniform and thin developer layer. At the same time, in the developing apparatus wherein the developer layer does not come in contact with and rub the surface of the image-forming member, it has proved that if the clearance for development is to be decreased, the developer layer is apt to come in contact with and rub the surface of the image-forming member, and that setting a narrow clearance for development which does not come in contact with and rub the surface of the image-forming member is difficult.